Currently, in order for holiday decorations, light strings of traditional LEDs (called light emitting diodes) are made into a lighting decoration product in the form similar to a string of small firecrackers, commonly known as a firecracker lamp. Disadvantages of such the firecracker lamp are: 1. lamp bulbs and lamp sockets on the light strings are large in volume, and conducting wires are relatively thicker, wherein when the number of lamp bulbs in series increases, the entire product has larger volume, resulting in that it is not easy to package and install the product; and 2. the waterproof property of the lamp bulbs and the lamp sockets is poor, therefore putting at risk to use it outdoor, and of course, not suitable to use underwater.